Battery building help

[Blunderbuss]

Having now built three ebikes I have realised that for me it is the battery that has been the biggest problem, I have spent far too long measuring and remeasuring to see if any will fit . I bought one that I knew would be snug, only to realise that the dimensions stated did not include the mounting rail – so it did not fit

All that has meant that I have decided to teach myself (through the usual trial & error methods) how to assemble a battery, because if I can do this then I can use almost any donor frame.

I have got to the stage where I need to connect the batteries together. I have spent quite a while practicing with a soldering iron and that is not working for me, too slow and too hit and miss (not saying it can’t be done just saying its not for me). So I started checking out spot welding, I saw a bloke on Youtube who had connected up some electrodes to a car battery and “shorted” them out to create a weld – tried that and it was all sparks , not consistent.

So now I am at the stage of possibly buying a spot welder (seen them for around £150 on ebay) I don’t mind spending the money as I am lucky enough to get the cells from old laptop batteries via work. But I have also seen the item below on ebay:

https://www.ebay.co.uk/itm/Kit-for-DIY-18650-Lithium-Battery-Pack-Spot-Welder-UK-Seller/302853370799?hash=item468377b3af:g:MuEAAOSwuOpbZZ7L

My progress so far is in the picture, it should/will be a 48v 14AH with the controller inside, the bit of carboard is the space in the frame and I have made the aluminium housing 20mm smaller all round so that it will fit (I will make a canvas bag for it to go in).

I would be very happy to hear from anyone who has experience of the spot welders or that kit above – thanks.

 

[anotherkiwi]

Having now built three ebikes I have realised that for me it is the battery that has been the biggest problem, I have spent far too long measuring and remeasuring to see if any will fit . I bought one that I knew would be snug, only to realise that the dimensions stated did not include the mounting rail – so it did not fit

All that has meant that I have decided to teach myself (through the usual trial & error methods) how to assemble a battery, because if I can do this then I can use almost any donor frame.

I have got to the stage where I need to connect the batteries together. I have spent quite a while practicing with a soldering iron and that is not working for me, too slow and too hit and miss (not saying it can’t be done just saying its not for me). So I started checking out spot welding, I saw a bloke on Youtube who had connected up some electrodes to a car battery and “shorted” them out to create a weld – tried that and it was all sparks , not consistent.

So now I am at the stage of possibly buying a spot welder (seen them for around £150 on ebay) I don’t mind spending the money as I am lucky enough to get the cells from old laptop batteries via work. But I have also seen the item below on ebay:

https://www.ebay.co.uk/itm/Kit-for-DIY-18650-Lithium-Battery-Pack-Spot-Welder-UK-Seller/302853370799?hash=item468377b3af:g:MuEAAOSwuOpbZZ7L

My progress so far is in the picture, it should/will be a 48v 14AH with the controller inside, the bit of carboard is the space in the frame and I have made the aluminium housing 20mm smaller all round so that it will fit (I will make a canvas bag for it to go in).

I would be very happy to hear from anyone who has experience of the spot welders or that kit above – thanks.

View attachment 26504

https://m.blog.naver.com/aulakiria/220992039512

https://www.keenlab.de/index.php/portfolio-item/kweld/

I am going to choose one or the other of these.

 

[Blunderbuss]

I saw these but got a bit confused as to what else you needed to make them work:

http://www.reuk.co.uk/wordpress/dual-pulse-spot-welder-timer-controller/

 

[Blunderbuss]

Whilst chewing over the spot welder question I also did a test on wiring in a front light and a USB charging port to my existing battery - I wanted to see if it would work and what the power drain was.

As the lights came in a pair I connected them both via a small £3 switch from B&Q:

https://www.amazon.co.uk/gp/product/B06XW3M8B9/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

The USB charger did say it was okay to 50V input, but at full charge my battery is 54.6V, so I hoped for a little bit of tolerance in the build!

https://www.amazon.co.uk/gp/product/B06XWLCBD7/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I did not use any other components, just a straight forward soldered joint to the main power wires.

I then switched on the lights and plugged my phone into the usb charger (phone was at 50% power, I also switched on the gps and set it playing some music) and left the whole thing running for 1 hour.

It used ½ volt from the battery in that time, which I am more than happy with (it is a 10AH battery) and my phone was also fully charged

Now just to decide on the spot welder.

 

[Blunderbuss]

In an impulsive moment i went on ebay and bought one of the spot welders, got it delivered yesterday and watched the various youtube videos from helpful people - and i am impressed. A few minutes trying out the settings (starting low and working up) and it is working a treat.

I now have in mind to make two identical batteries that i can connect together so that i will have a 10AH and 20AH configurations available.

 

[anotherkiwi]

Good on you! d8veh has one of those IIRC besides the price what put me off is they can be a bit of a lottery. They can be easy to fix/upgrade from what I have read on ES.

I saw these but got a bit confused as to what else you needed to make them work:

They need a high discharge 3S or 4S LiPo brick, one capable of +130A burst discharge. As I already have LiPo and chargers and whatnot they make economic sense especially the Korean one at $85 or so.

 

[wheeliepete]

I've had one of those welders for a couple of years and is still working OK having built around 10 battery packs. The soldering iron died on mine quite quickly and the remote welder does not have the power of the fixed probes, but I think it has just about paid for itself. Top tip, if you put a bend in the probes it allows you to weld 3 cells deep which can be useful on 5/6P packs. I think I put them in a vise to do this so not to damage the welder. Don't forget to wear some eye protection and remove rings, watches, etc. It is real easy to short out the wrong parallel cells, esp. when you are welding the second side of the pack. You want to avoid KFF! Have fun!

 

[Blunderbuss]

I've had one of those welders for a couple of years and is still working OK having built around 10 battery packs. The soldering iron died on mine quite quickly and the remote welder does not have the power of the fixed probes, but I think it has just about paid for itself. Top tip, if you put a bend in the probes it allows you to weld 3 cells deep which can be useful on 5/6P packs. I think I put them in a vise to do this so not to damage the welder. Don't forget to wear some eye protection and remove rings, watches, etc. It is real easy to short out the wrong parallel cells, esp. when you are welding the second side of the pack. You want to avoid KFF! Have fun!

Thank you for the tip, I will do that with electrodes I can see how getting that extra reach will help. I have had a quick go with the remote welders and like you say they just don’t carry the juice!

I hunted down KFF and have decided to slow down a bit – set things up properly. I never thought that could happen, but it makes sense as the pack gets bigger and more unwieldy. Consider that an excellent thing to share and a great way to do it – very much appreciated. Now off to have safe fun